a) Field of the Invention
The present invention relates to a dumping semi-trailer. The invention relates further to a dumping semi-trailer having a middle axle.
b) Brief Description of the Prior Art
Semi-trailer dump trucks are a known variety of dump trucks having the dump body provided on a semi-trailer frame. When the dump body is made very long, as is often the case in semi-trailer dump trucks, the tilt mechanism, usually a hydraulic cylinder, must be specially adapted to lift the long dump body through a great distance in order to dump the contents of the dump body.
Canadian Patent 695,573 describes using a single articulated arm to facilitate tilting of the dump body. The articulated arm is connected between a base of the hydraulic cylinder located at the front of the dump body and the central part of the bottom of the dump body. In this way, the cylinder can extend through a distance about forty percent less than in the case when the dump body is pivotally attached at the rear of the rigid base-frame.
The single articulated mechanism described in Canadian Patent 695,573 was improved by the addition of a second articulated arm member, as described in Canadian Patent 841,484. The second articulated arm member interconnects between the first articulated arm member and the rear base frame of the rear axles of the semi-trailer dump truck. The second articulated arm member acts to maintain the rear frame horizontal, thus helping to maintain both rear axles level and on the ground during the articulated lifting process.
The current versions of the semi-trailer dump mechanism described in Canadian Patent 841,484 work smoothly and efficiently for small, light loads. However, it is desirable to extend the length of the semi-trailer dump body and to increase the carrying capacity as this would lead to greater efficiency. Extending the length of the semi-trailer dump body, thereby increasing the maximum possible load to be carried by the dump body, cannot be due to the restrictions on maximum axle load capacities, as determined by the highway authorities. The present length of the semi-trailer dump bodies can also be extended without exceeding the maximum legal limit for the length of a semi-trailer body.